Magnetic material and manufacture thereof



Patented June 29, 1931 MAGNETIC MATERIAL AND MANUFACTURE THEREOF FranzNoll, Berlin-Siemensstadt, Germany, as

signer to Siemens and Halske Aktiengesellschaft, Siemensstadt, nearBerlin, Germany, a

company of Germany No Drawing. Application July 28,

No. 682,669. In Germany August 5 Claims.

This invention relates to magnetic alloys of the nickel-iron type and anobject thereof is to achieve magnetic alloys and methods of manufacturethereof which have a high constancy of permeability at low magnetizingforces together with a high specific resistivity and a permeabilitysufiiciently high for use in loading coils and similar magnetic devices.

The present. invention relates to the class of magnetic alloys used inthe cold rolled condition and more particularly to those having '30 to50% nickel, 4 to 11% copper, 1 to 7% manganese and the balanceessentially iron. It has been found that these alloys have the propertythat after a cold working treatment which reduces them in cross-sectionto or less of the cross-section before working that they show not only areduction in hysteresis losses but an increase in the permeability atvery low magnetizing forces.

It is an object of the present invention to provide compositions whichhave magnetic properties similar to those mentioned in the foregoingparagraph but of higher specific resistance.

It is also an object to provide magnetic alloys otherwise desirable inwhich the permeability is practically linear for a range tr magnetizingforces up to as high as 3 Gauss.

According to one feature of the invention the magnetic alloys have acomposition of over 30% Ni and over 1% Mn, remainder iron and are usedin cold-treated condition. Preferably the nickel content amounts tobetween 30 and 50%, and the manganese content over 6% to 25%.

.These alloys with up to 11% manganese showed special advantages. 7 a

The cold-treated materials are worked into a 1933, Serial that is, forexample. in Krarup conductors the cold-rolled band is spiralled upon theconductor, without previous annealing of the band. The wrapped Krarupconductors also are not annealed before their insulation and applicationin the cable. In the manufacture of band and wire cores, for example,for Pupin 'coils, the

The mechanical treatment of the mag- A magnetic alloy of,;for example,50% nickel,

39% iron and 11% manganese, is rolled, with intermediate annealing, intoa round wire of 4 mm. cross-section. After annealing, the wire isbrought by drawing or rolling to a square crosssection with 1.2 mm. edgelength, and thereupon rolled into band form without intermediateannealing, to a thickness of 0.08 mm. and a width of severalmillimeters. The reduction of thickness without intermediate annealingamounts in this case to of the original thickness. The tape or,strlp isthen ready for the wrapping of a conductor or for winding in the formofa core. consisting of strips bound together. The following table showsthat with increasing cold working, not only does the hysteresis lossdrop, but the permeability rises. The alloys are characterized by anextremely small rise in permeability as the magnetizing force increasesin the range of field intensity chiefly form for use without a finalannealing process, used for weak current purposes.

Band Field in which fill!!! M0 nun. tically o. 15 7a 200 1. a o. nozsNilfiunnsidue Fe 2% 0'86 86Ni-3Mnmidnc Fe 3g 2 & grg on 36Ni6MnlesidneFe :52: Z; :33 F: o. as N10 Mn residue 1b.. gfi g g a. flNiiMnmldmFe &%g g M1 1' iulqiflllnrcliduc c um 7 no. 3' I Thealloys indicated in thetable were rolled to a cross-section of 4 mm. diameter and thereuponannealed at 800 C. for about two to three hours in a hydrogen atmospherebefore being finished by rolling and drawing.

The. table shows in the first column the composition of the alloys, inthe second column the thickness to which the strips or tapes arebrought, the third column the initial permeability measured in annularcore form, the fourth column the hysteresis constant, and the fifth col-1 umn the field in which the rise of permeability The last column,

can be regarded as linear. finally, gives the ohmic resistance.

A further feature of the invention comprises magnetic materialscontaining 30% to 50% nickel, 4% to 11% copper and 1% to 7% manganesewith the balance essentially iron.

a A following table shows by several examples theproperties of theiron-copper-nickel alloys with an addition of manganese if a. coldworking treatment, such as previously described, is employed. Themeasurements given below are made on toroidal core coils of bands.

Thickness Specific Composition of band n h resistance From the table itwill be seen that even withv the addition of manganese toiron-nickel-copper alloys extremely low values of the hysteresisconstant can be obtained with relatively high initial permeabilities. Intwo of the alloys cited it is shown that by increasing the degree ofworking an improvement is obtained both in the initial permeability andalso of the hysteresis constant. v Although an increased specificelectrical resistance is obtained by the manganese content,

by further small additions of chromium, molybdenum, tlmgsten, vanadiumand similar substances, a further increase in the specific resistance ofany of the alloys herein mentioned. can be effected withoutsubstantially impairing-the magnetic properties.

What is claimed is:

l, A method of preparing magnetic material of the class including alloysof 30 to 50% nickel, 1 to 11% manganese and the balance chiefly iron,

but not excluding minor proportions of other metallic substances, whichcomprises rolling the material with intermediate annealing into a roundwire, annealing the said round wire in a hydrogen atmosphere atapproximately 800 C., co'ld drawing and rolling the wire into a squarecross-section, and then rolling it without intermediate annealing intoband form, the crosssection of said band being less than 6 of thecross-section possessed by the material before the cold working.

2. An article of manufacture comprising magnetic material in the form ofan elongated strip and in final form foruse, said material beingcomposed of an alloy comprising 30 to 50% nickel, 1 to 11% manganese,and the balance chiefly iron but not excluding minor proportions ofother metallic substances characterized in that the strip, afterannealing at a high temperature,

has been forcibly elongated as by rolling or drawing in the cold stateas the final step of its manufacture, 'sufliciently to reduce itscross-section below of the cross-section possessed by it before the coldworking.

3. A magnetic material in finalphysical form for use consisting of analloy of 30 to 50% nickel, 4- to 11% copper, l to 7% manganese, and thebalance chiefly iron, characterized in that the material has first beenannealed at a high temperature and then put into final form for use by atreatment in which the final step of its manufacture consists of aforcible elongation. of the material to such an extent that itscross-section is reduced to below of the cross-section possessed by itbefore the cold working.

4. A method of preparing a magnetic material composed of 30 to 50%nickel, 1 to 7% manganese, and the balance chiefly iron, whichcomtemperature above the magnetic transition temperature andsubsequently as the final step of its perature above the magnetictransition temperature and subsequently as the final step of itsmanufacture reducing the material to a physical form suitable for use'bya process of cold rolling to reduce its cross-section tonot more than ofthe cross-section before the cold rolling.

FRANZ NOLL.

.prises annealing the material in hydrogen at a

